I purchased a 2009 Fiesta 3 months ago and in the early days I noticed crackling when driving around, especially over speed bumps and poorly surfaced roads. I tightened up the aerial thinking that would do the trick. Then having not used the car for a week or so I noticed it again. It'son all stations across the band, such as 5 Live and Talksport, so it is nothing to do with signal strength as they are all pretty high power with good reception in the area where I live (west London).

In an attempt to sort it out I took off the aerial and thoroughly cleaned the male and female connectors to remove any possible corrosion. I then applied vaseline and tightened it up. Hey presto it seemed to work the next time I went out on the road - crackling gone. However, not a happy ending because the 3 month warranty is due to expire this weekend I did a final check and the crackling has re-appeared.

I can replicate the crackling by moving the aerial up and down manually with the engine switched off, so to me, that rules out everything not aerial related.

I took the car in today to Dagenham Motors and they say that they cannot find the cause, however I am not convinced that they quite get it. The person who booked in the car says it's because it's AM however being a former radio amateur who knows a bit about broadcast reception I think that as it's not something that has a computer diagnosis they are out of their depth.